Micro-electro-mechanical system (MEMS) devices may be used in various applications such as micro-phones, accelerometers, inkjet printers, etc. A commonly used type of MEMS devices includes a MEMS capacitor that has a movable element as a capacitor plate, and a fixed element as the other capacitor plate. The movement of the movable element causes the change in the capacitance of the capacitor. The change in the capacitance may be converted into the change in an electrical signal, and hence the MEMS device may be used as a micro-phone, an accelerometer, or the like. The movement of the movable element may also be used in an inkjet printer for squeezing the ink.
MEMS devices typically require a cap capping the MEMS devices for protection purpose. The bonding may be performed through eutectic bonding. However, the bonded surface may have an oxide layer that adversely affects the reliability of the bonding, and the oxide layer needs to be removed before bonding.